Merc 25 won't start

take several pics of your carb and the attached linkage for reference when re assembling it... remove carb, carefully remove covers from carb then flood with carb cleaner then reassemble. i've done this to both of the 2003 mercs i've had and worked like a charm both times

 

. be very carefull when pulling the side covers and bowl off the carb. if i'm not mistaken there was a jet or ???? thats lose and if your not ready for it when you pull the cover off it might go flying just take your time and work over a clean surface and you should be ok i've had 2 of the 03 25 hp 2 strokes motors that developed fuel related issues and after a good hosing down of some carb cleaner they both ran like scalded dogs ;D

 

disconnect the kill switch wires. theres two of them, try one at a time. those things only last like 3-4 years

 

You did REPLACE the filter (assuming it is more than just a metal screen in the fuel pump), right? I'm not an outboard tech by a long shot (fair warning), but an engine is an engine is an engine.  I've worked on many,many of them.  They all need fuel/air, compression, and ignition. 

1) Check to see if you have enough fuel in your tank for the pick up.  No I'm not being a jerk, it happens to the best of us.  As suggested check your kill switches, by pulling out he safety lanyard and reinserting the clip.  I've had mine walk out enough to break contact, but not fall out.  Check to see if main ignition switch/key is in the on position.  You will feel like an idiot if it is one of these, but it is better than going though steps 2-5 and then finding out.

2) Check to see if fuel flows though the fuel line.  Disconnect at motor and connect to a spare male connector.  I have one to fill up my 2 smoke yard tools.  I keep it in the boat for emergencies (fuel transfer etc). I've never needed it so far.  Replace fuel line and hand pump as needed.

3) Squirt a small amount of fuel into your carb(s) and crank the motor.  You may have to pull cowlings covers off to do this.  I have used starter fluid in the past, but I've been told that is a no no with outboards.  Use at your own risk.  If it cranks for a second or more and dies, repeat.  If it does it again, stop and do a happy dance, then try to figure out what good deed you did to deserve your good fortune.  I say this because I'd say your fuel pump needs rebuilding or the carbs are gummed up (debris, stuck float, etc.) and those are pretty easy fixes.   Clean carb(s) first and then rebuild pump as needed.  I tend to pull and clean my carb at least once a year as part of maintenance anyway.  Don't get me started on ethanol and old gas.

4) Check spark.  This can be tricky and misleading BTW.  Label and  pull the plug wires off all plugs by pulling on the rubber boot, not the actual wire.  Use purpose made pliers if needed.  Pull the plugs (check/clean/gap them while you are at it).  Attach a plug back into one wire and have someone you really don't like hold the plug and the crank the motor, you'll know if you have spark (I suggest having your running shoes on before you start).  J/K!  That hurts like hell, ask me how I know.  Really, use a fancy tool like what is basically a spark plug with an alligator clip welded to it or one of the other styles of spark checkers.  If you don't have one use a regular old spark plug, just make darned sure you ground it out. You can use a pair of insulated pliers for that (if I can't find my tool, I do this but wear a heavy duty glove as well).  If you are lucky, you can sometimes lay the plug onto the engine.  I'm never that lucky.  Trust me you do not want to get hit by this, since the plugs are out of all cylinders, that engine will spin like a top and you can't let go till it stops.  Can you say tazer?  You should see a bright pulsing spark (period is dependent on RPMs), even in daylight.  Here is the tricky part.  If you don't have a good bright spark it could mean you have a bad plug, wire, coil/power pack, or any other part of your ignition system.  OR, you may have not grounded out the plug/tester right.  If you get a weak spark see above.  Repeat with all cylinders.   Having fun yet?  Switch plugs with another one, if they are old replace with new ones since you were going to do that anyway, right?  Ditto with the wires.  If you still can't get a good spark, it may be a coil/power pack.  If you have two coils/power packs, chances are one will still be good (so you can see the difference), but they can both go at the same time.  I'd take the "bad" one(s) to a shop and have them test it.  After that get a manual and check the rest of the ignition system.  That usually involves pulling the fly wheel, oh joy.  You may want to go to the next step before you do that.

5) Do a compression test.  I like to at least pull all of the plug wires before doing this, so the motor can't start (because you know it will when you don't want it to).  Look up what #s you should have.  I don't need to tell you how bad it is if your motors compression is bad.

I tend to do a compression test half way though step #4 just so I don't tear into more than I need to. If none of that works seek professional help, both for the motor and your sanity.  Oh and if you don't have one already, get a repair/maintenance manual.  BTW the advice about checking the safety features is a good one.  That is right up there with checking if you have fuel. If you have direct injection, I know some of those have fail safes (may shut off ignition) on them, but I'm not familiar with them.  Maybe someone else will pipe in on those if applicable.

Hope it helps.

Swamp

 

Oh Forgot to say you could have water in your fuel system. Go though step #3, but check to see if you have water (may look look a tan oily sludge) in your carb bowl when you clean the carb. Some carbs can be drained without removal, catch and inspect the fluid. The fuel pump may be fine then. Drain and refill fuel to solve the problem. I'd pull and clean the carb anyway.

 

Good for you.  Happy dance time! [smiley=chicken.gif]

 

thats awesome where should we send the bill? ;D

 

Did you mix older fuel with e-10 fuel and leave it sit for awile ?